1. Field of the Invention
The present invention relates to a support-frame bonding apparatus for bonding a support frame to a semiconductor device mounted on a tape-automated bonding (TAB) tape such as a tape ball grid array (T-BGA). Particularly, it relates to a support-frame bonding apparatus which can realize a satisfactory bond without causing voids in the adhesive, regardless of the shape of the semiconductor device or the support frame.
2. Description of the Related Art
There is an increasing demand for the reduction in size and increase in density of semiconductor devices. In response, surface-mounting semiconductor devices such as ball grid arrays (BGA) are being used with increasing frequency. Of those BGAs, ones employing as a package material a TAB tape in which a wiring pattern is formed are called T-BGAs. Generally, a T-BGA is used with a support frame attached to it which is formed of a copper plate, for example, for the purposes of improving mechanical strength and reducing thermal resistance.
When attaching such a support frame to semiconductor devices such as a T-BGA, a support-frame bonding apparatus is used whereby the frame and the semiconductor device are bonded to each other by an adhesive through a high-temperature pressure bonding process. In accordance with the conventional bonding apparatus, a T-BGA, for example, is placed on the support frame on which an adhesive layer is formed, and the two members are pressed against each other by heated metal plates to thereby establish a bond. Such conventional support-frame bonding apparatus, however, has the following disadvantages. That is, neither the support frame nor the semiconductor device is always flat; they are often warped on the edges. Furthermore, the semiconductor devices such as T-BGAs, on which semiconductor chips and wirings are mounted, have irregular surface profiles. These facts result in a failure to uniformly apply the bonding pressure by the metal plates. So, some portions of the device and/or the support frame are in a failure to receive enough bonding pressure. Such portions tend to cause quality defects including voids in the adhesive and separation between the semiconductor device and the support-frame. If there are voids in the adhesive, they can burst during the high-temperature test in the inspection step, causing the semiconductor device to be peeled from the support frame.
To overcome those problems, it has been proposed, as disclosed in Japanese Patent Laid-Open Publication No. Hei. 11-163212, to attach an elastic member to the metal plate for pressing the semiconductor device and support frame, so that the bonding pressure can be uniformly distributed.
Yet this counter-measure also has the disadvantage that after the semiconductor device has been pressure-bonded to the support frame, the elastic m often sticks to and remains on the semiconductor device and/or the support frame, possibly causing operational failure in the support-frame bonding apparatus.
Accordingly, it is an object of the present invention to provide a support-frame bonding apparatus which can bond the support frame to the semiconductor device such as a T-BGA without causing the elastic member for the uniform distribution of bonding pressure to be attached to either the semiconductor device or the support frame.
The support-frame bonding apparatus according to the present invention bonds, via an adhesive layer, the support frame to a semiconductor device mounted on a TAB tape. The support-frame bonding apparatus comprises at least one of an elastic member, a pressing unit and a heating unit. The elastic member has a satin finish on its surface. The pressing unit presses the semiconductor device, the adhesive layer, the support frame and elastic member each other. The semiconductor device and the support frame are superposed via the adhesive layer. The at least one of elastic member is provided to at least one of the outer surfaces of the semiconductor device and the support frame which are not the superposed surfaces of the semiconductor device and the support frame so as to contact the satin finish surface with the outer surface of the semiconductor device or the support frame. The heating unit heats the adhesive layer to bond the semiconductor device to the support frame via the adhesive layer.
In the present invention, the elastic member with a satin finish provided thereon helps to prevent the sticking of the elastic member to the semiconductor device and/or the support frame after bonding the support frame to the semiconductor device, as well as helping to uniformly distribute the bonding pressure applied to the adhesive layer.
The pressing unit may comprise a first pressing member for retaining the support frame, a second pressing member for retaining the semiconductor device, and a pressure applying unit for applying pressure to the first and second pressing members such that the first and second pressing members get closer to each other. In this case, the elastic member is placed in at least one of the portions between the first pressing member and the support frame and between the second pressing member and the semiconductor device.
Preferably, the elastic member may be formed of a material which is heat resistant and conductive. For example, it can be formed of a conductive silicon rubber. The conductive silicon rubber is heat resistant, so that it can be repeatedly heated without deterioration. Since the silicon conductive rubber is electrically conductive, it does not generate static electricity, thus preventing the attaching of the rubber to the semiconductor device or the support frame due to static electricity. The absence of static electricity also means that the semiconductor device is not damaged by such static electricity.
The adhesive layer may be formed on the support frame in such manner that, when seen from above in a plan view, the outline of the area of the elastic member that comes into contact with the semiconductor device or support frame lies inside the outline of the semiconductor device, and may be at the same time identical to or lying outside the outline of the area of the adhesive layer formed on the support frame.
Semiconductor devices such as a T-BGA might be greatly deformed at their edges during the pressure bonding process. Such deformation may not be fully accommodated by the elastic member. Consequently, there may arise voids in the adhesive at the edges of the semiconductor device, or the semiconductor device may peel off the support frame. These problems are addressed by the present invention whereby the outline of the area of the elastic member that comes into contact with the semiconductor device or support frame is smaller than the outline of the semiconductor device. This insures that the elastic member does not contact the potential warping at the edges of the support frame or the semiconductor device, even when the warping is large. Accordingly, the elastic member can function to uniformly apply bonding pressure to the adhesive layer. On the other hand, by specifying that the outline of the contacting area of the elastic member is identical to or larger than the outline of the adhesive layer, the support-frame bonding apparatus can apply a more uniform bonding pressure to the edges of the adhesive layer.